I. Field of the Invention
This invention relates generally to machines for feeding sheets one at a time from a stack of such sheets contained within a hopper, and more particularly to apparatus for automatically filling the hopper as the supply of sheets therein becomes depleted.
II. Discussion of the Prior Art
So-called friction feeders, sheet feeders and shingle feeders are known in the prior art. These machines are designed to dispense sheets from a stack of such sheets contained in a hopper, one at a time, to an output conveyor for collating and/or packaging the sheet products. When dealing with printed matter, there may be a sheet feeder for each page to be assembled into a booklet and, therefore, many such identical sheet feeders may be positioned adjacent the discharge conveyor for depositing a different sheet or page as the booklet is being assembled.
A typical sheet feeder will have an endless belt running beneath a hopper that frictionally engages the bottommost sheet in a stack of sheets in the hopper and carries it through a gap defined by a gate member, the gate member serving to hold back all but the bottommost sheet until that sheet clears the gap. For such a sheet feeder to work on a continuous basis, there is a limit to how many sheets may be contained in a stack in the hopper. The weight of the sheets in the stack is a factor in how well they can be fed without jamming. Because there is a limit to the number of sheets that may be stacked in the hopper for delivery, an individual attendant can only service a few such feeders.
Recognizing this problem and in attempting to reduce manpower costs, automatic product loaders have been developed for feeding sheets products into the hopper of the friction feeder on an "as needed" basis. The Golicz U.S. Pat. No. 4,772,004 describes a feeder mechanism in which a first endless belt conveyor is used to feed a stack of sheets onto a second endless belt disposed below the plane of the first belt. The sheets on the second belt are brought into contact with a specially designed gate structure referred to therein as a "singulator feeder assembly".
The apparatus described in the Golicz '004 suffers from several drawbacks. First, it lacks proper product guiding from the loader conveyor to the infeed conveyor such that sheets are likely to become skewed. Also, it lacks support for holding the stack of products proximate the trailing edge thereof to thereby minimize the weight of the stack on the feed belt. Without such a rear support element, proper shingling of products passing beneath the singulator does not occur, leading to unwanted multiple sheet feeds.
Disclosed in a co-pending Vedoy, et al. patent application Ser. No. 09/032,825 entitled "Sheet Feeder" and assigned to the assignee of the present invention is an electronically controlled sheet feeder having a hopper defined by front guides 28 and 30, a rear support 78 and first and second parallel spaced-apart side plates 84 and 86. (The contents of that patent application are hereby incorporated by reference as if fully set forth herein.) The present invention provides an improved automatic product loader for use with such a sheet feeder whereby a large quantity of sheet products may be continuously loaded from the automatic product loader into the hopper of the friction feeder. As such, a single attendant is readily able to maintain a supply of sheet products to be singulated on a large plurality of sheet feeder systems.